1. Field of the Invention
This present invention relates to the fabrication of a semiconductor device, and more specifically to a semiconductor device fabricated from silicon on insulator, (SOI) technology.
2. Description of Prior Art
The objective of the semiconductor industry is to continually decrease the cost of manufacturing semiconductor chips, while still increasing the performance of these same chips. Micro-miniaturazation, or the ability to create shapes and images with sub-micron dimensions, has allowed these objectives to be partially realized. Advances in specific semiconductor disciplines, such as photolithography, via more sophisticated exposure cameras, as well as more sensitive photoresist materials, have allowed sub-micron images, in photoresist layers, to be routinely obtained. In addition similar developments in the dry etching discipline has allowed these sub-micron images in photoresist to be accurately transferred to underlying semiconductor materials, used for the fabrication of advanced devices. The creation of sub-micron shapes allow for the fabrication of smaller chips, resulting in more chips per wafer, and thus reducing costs. In addition smaller shapes result in a decrease in junction capacitance, as well as specific resistances, thus also improving device performance.
Although micro-miniaturazation has allowed the cost and performance objectives to be partially met, the semiconductor industry continues to evaluate additional methods to surpass these objectives. The development of silicon on insulator, (SOI), has resulted in significant performance improvements, when compared to counterparts fabricated using conventional processes. The SOI technology, in which devices are fabricated in a thin layer of silicon, which in turn overlies an insulator, removes a large portion of the diffusion to substrate parasitic capacitance, thus resulting in device performance benefits. Metal oxide semiconductor field effect transistors, (MOSFET), have been fabricated using SOI concepts. For example Houston, et al, in U.S. Pat. No. 5,185,280, as well as Iwamatsu, et al, in U.S. Pat. No. 5,294,281, have described methods for fabricating MOSFETs using SOI. However specific fabrication steps, needed to contact specific regions of a MOSFET device, to avoid deleterious device characteristics, have not been shown. For example a MOSFET fabricated without direct contact to a channel region, or with a body floating, will experience a "kink" effect, or suffer from a low, source to drain breakdown voltage, BV.sub.ds. MOSFETs fabricated with body contacts, in the past, have added considerable complexity and cost to the process, in terms of additional layers. This invention will describe a process for providing a body contact to a MOSFET chip, by only including a masking and ion implantation sequence, to the MOSFET fabrication process flow.